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1.
刺胞动物是华南寒武纪早期海洋生态系统的重要组成部分,针对这类化石的研究有助于深入了解寒武纪多幕式爆发事件。本文主要根据寒武纪早期扬子板块陕南宽川铺生物群、湖北岩家河生物群以及澄江生物群产出的刺胞动物,探讨刺胞动物在寒武纪早期的演化框架,取得了以下初步认识。截至目前,所发现的寒武纪早期刺胞动物绝大多数都属于水母超纲,珊瑚纲的化石记录在寒武系幸运阶、第二阶保存较为罕见。其中寒武系幸运阶刺胞动物的化石记录全部属于底栖类型,体型小,且具有多种类型的身体辐射对称形式,绝大多数类型可以确定属于直接发育。第二阶刺胞动物仍以底栖固着类型为主,体形增大,仅见两、四辐射对称形式;而寒武系第三阶刺胞动物仍有底栖固着类型,但游泳的水母开始出现,体型增大明显,代表水母冠群的出现,以及世代交替的复杂生命周期的正式建立。从幸运阶到第三阶刺胞动物体型明显增大,可能与海水氧气含量增加有关。在寒武纪大爆发的背景下,刺胞动物的分异度和丰度在寒武系幸运阶就已经达到顶峰,然后在第二阶、第三阶开始衰减,这种变化可能与两侧对称动物辐射演化有关。华南刺胞动物的化石记录表明,寒武纪大爆发并非纯粹的一幕式爆发,其中充斥着一系列生物群的替代甚至灭绝事件。 相似文献
2.
澳大利亚寒武系生物地层研究新进展(英文) 总被引：1，自引：1，他引：0
澳大利亚寒武系集中分布在一南北向分布的从澳大利亚的北部、中部直到南澳大利亚克拉通地块上,少量寒武纪地层分布在新南威尔士、维多利亚和塔斯马尼亚。寒武系的底在中澳大利亚的Amadeus盆地出露得最好。下寒武统(大致相当于纽芬兰统和第二统)在澳大利亚北部大多数是不含化石的火山岩,而在澳大利亚中部和南澳大利亚的盆地中,其中最有名的是南澳大利亚的Arrowie和Stansbury盆地则是各种含化石的巨厚沉积序列。澳大利亚的下寒武统没有分阶方案,尽管在生物地层研究上最近取得很大进展,现在可以利用疑源类、遗迹化石、古杯类、三叶虫、腕足类、软体动物和其他小壳化石进行化石带的划分。很长一段时间内澳大利亚中部和北部的Ord-ian阶被认为是中寒武世最早期的,现在证明它可能相当于第二统的全部或者一部分;含化石的中寒武统和芙蓉统(或上寒武统)在Georgina盆地东部发育非常完整,在中澳大利亚、新南威尔士、维多利亚和塔斯马尼亚也可见到,都可以划分到阶。芙蓉统的底大致与Idamean阶的底相当。化石带的建立主要综合考虑球接子三叶虫、多节类三叶虫,自Iverian期晚期起再加上牙形类化石。寒武系的顶大致相当于Warendan阶的底,相关地层在Georgina盆地东部发育得很好。 相似文献
3.
选择层型剖面,确定前寒武系——寒武系界线,是目前国际地层学领域中的重大课题之一。本文主要介绍我国近年来研究小壳化石组合及遗迹化石序列的成果,指出这些成果对确定国际及我国震旦系——寒武系界线的重要意义。文中简略回顾了我国研究寒武纪最早期带壳化石及震旦系——寒武系界线的历史,指出我国是开展这一学科的较早的国家之一,而滇东又是它的发源地。对小壳化石的涵义进行了厘订,认为必须赋以时代概念。建立了我国梅树村阶的三个小壳化石组合,讨论了它们的特征及主要组成。首次建立了我国梅树村阶遗迹化石序列的四个序次,代表古陆边缘浅水环境中含磷岩系的遗迹化石序列,讨论了它们与带壳化石及其它化石之间的联系,并就其中发现的具有全球性对比意义的二属,阐明梅树村阶遗迹化石序列的重要地位。最后,作者根据地科联前寒武系——寒武系界线工作组确立的原则,讨论了中国震旦系——寒武系界线的划分和对比。文中对小壳化石来划分这条界线的理论根据、“爆发式”出现的理解以及生物带壳演化的原因和同时性进行了概略的讨论。并提供了含小壳化石地层的同位素年龄、古地磁测定资料。 相似文献
4.
综合分析世界各地区,特别是扬子地台和西伯利亚地台前寒武系—寒武系界线层中的早期骨骼化石,可以看出早期骨骼动物的演化可自老至新分三个阶段。第一阶段为Anabarites-Protohertzina动物群,相当于扬子地台梅树村阶的Anabarites-Protohertzina带和西伯利亚地台马内凯阶的A.trisulcatus带和P.cristata带。第二阶段为早期直管螺形类和软体类动物群,相当梅树村阶Paragloborilus-Siphogonuchites带和托莫特阶Aldanocyaihus Sunnagintcus带。第三阶段为早期软舌螺形类和拉普沃斯壳类动物群,相当梅树村阶的Sinosachitos带及托莫特阶D.regularis带和D.lenaicus带。早期骨骼动物演化的三个阶段可作为洲际对比的标志。 相似文献
5.
Shehryar Ahmed 潘兵 Malik Muhammad Saud Sajid Khan 李国祥 Muhammad Qasim 罗翠 孙晓娟 朱茂炎 《地层学杂志》2023,(3):339-352
小壳化石是寒武系纽芬兰统年代地层划分和全球对比的主要生物地层学依据。长期以来,喜马拉雅西侧的巴基斯坦北部寒武纪早期小壳化石的发现较为零星,导致该地区埃迪卡拉纪与寒武纪过渡期地层序列的划分缺乏统一认识,相关地层时代归属十分不清晰。在第二次青藏科考任务的支持下,作者对巴基斯坦北部隶属于小喜马拉雅区的Hazara盆地东部前寒武纪与寒武纪过渡期地层Hazara组、Kakul组、Abbottabad组和Hazira组开展详细研究,首次在Kalu-di-Bandi剖面Abbottabad组Sirban段顶部硅磷质白云岩中发现了寒武纪纽芬兰世幸运期小壳化石组合。该小壳化石组合属种相对丰富,含有Anabarites trisulcatus、Protohertzina anabarica、Conotheca subcurvata、Hexangulaconularia formosa、Olivooides multisulcatus、Maikhanella pristinis、Lopochites latazonalis、Siphogonuchites sp.及Spirellus columnaris等分... 相似文献
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本文简要报道了1987—1988年间对梅树村剖面在岩石地层、生物地层及年代地层学等方面深入研究所取得的最新成果。重点对产于梅树村阶顶部的拉普渥斯壳(Lapworthella)进行了显微结构研究,特别是在中谊村段发现具有对比意义的遗迹化石Phycodes pedum Seilacher,玉案山段发现激江动物群的蠕形动物,水母和节肢动物.对梅树村阶的化石带作了补充。根据同位素年龄测定的最新结果,提出前寒武系-寒武系界线年龄值为597Ma。进一步讨论了“B”点仍是划分前寒武系—寒武系界线的最佳选择。 相似文献
7.
1986年笔者等在大连棋盘磨等地的金县群兴民村组中部王家坦页岩段页岩层中发现后生动物类水母化石;在金州北山等地的葛屯组页岩层中发现类水母化石、蠕虫化石、可疑小壳类化石和后生植物宏观藻类化石等,丰富了我国震旦系的古生物学内容,对辽南震旦系—寒武系界线的厘定提供了古生物学依据。 相似文献
8.
对湖北宜昌地区滚子坳剖面寒武系纽芬兰统幸运阶顶底界线的位置进行较为细致的研究.通过切片法及酸蚀法对61个样品进行系统处理,获得了大量的小壳化石、疑源类化石及其他分类位置未定化石.系统鉴定和描述了23属44种.根据具刺疑源类化石Asteridium和小壳化石Protohertzina sp.的首现位置以及无机碳同位素BACE曲线最大负值位置可以推断出埃迪卡拉系-寒武系界线应该位于第1层底部往上约10.5 m处;根据Zhijinites longistriatus的首现位置以及无机碳同位素ZHUCE曲线最大值位置可以推断出幸运阶与第二阶的界线位置大致为第4层底部往上约2.78 m.此外,还将峡东地区的小壳化石Ⅱ带和Ⅲ带重新定义,即将Purella antiqua组合（Zone Ⅱ）修订为Purella antiqua-Siphogonuchites triangularis组合;将Aldanella yanjiahensis组合（Zone Ⅲ）修订为Aldanella yanjiahensis-Zhijiniteslongistriatus组合. 相似文献
9.
近年来随着“鄂宜页1井”高产气井的突破,寒武系水井沱组(第2统第3阶)已成为中扬子区页岩气勘查开发新的主力层系。本文旨在前人研究的基础上,通过对水井沱组中主要生物类型、古生物组合面貌及其时空分布的简要总结,为鄂西地区的页岩气勘探提供对比借鉴。宜昌地区寒武纪地层发育完整,广泛出露于宜昌、秭归、长阳、兴山等地,古生物化石较为丰富,是开展寒武纪地层及古生物研究的经典地区之一。埃迪卡拉纪—寒武纪过渡时期的地质记录中保存了寒武纪大爆发和后生动物多样化事件的化石证据,从寒武系纽芬兰统到第二统,自下而上发现了岩家河生物群、水井沱生物群(包括清江生物群)、石牌生物群和京山布尔吉斯页岩型生物群等,它们化石类群多样,浮游生物和底栖生物丰富,而在长阳发现的清江生物群更是具有典型布尔吉斯页岩型动物群特异埋藏化石库的特点,出现了大量高保真度的软躯体类群,代表了远离海岸的较深水环境,为寒武纪大爆发研究打开了一个新的窗口。从岩性、生物类型以及构造运动来看,宜昌地区水井沱组发育一套以黑色页岩或钙质页岩夹碳质灰岩为主的黑色岩系,其中海绵化石在黑色岩系中呈现出较高的丰度和多样性,显示当时深水低氧的沉积环境。同时繁盛的微体... 相似文献
10.
基本重要性目前寒武系—寒武系界限成为颇专门的研究课题以来,所提出确定界限的建议是根据其地质或物理特征,而不是纯粹根据古生物准则。然而,很明显,只有生物地层准则可导致问题得以解决,用这种晚前寒武纪和寒武纪的生物区系之间意义深长的差异,有必要采用“前寒武系—寒武系层型点放在实际上接近产生托莫特(广义的)化石组合的最老地层单位底部”的原则,这是基于界限应沿着产生大量骨骼化石的最早一个带组合底部的想法建立的。既然是这样,古杯纲、腹足纲、软舌螺纲、托莫特壳类和鳃足亚纲即属此带组合。 相似文献
11.
《Gondwana Research》2014,25(3):999-1007
Abundant data have been acquired on the lower Cambrian small shelly fossils (SSFs) of the Yangtze platform during the last three decades, demonstrating that these fossils are an important piece of evidence for the Cambrian radiation and are useful biostratigraphic tools for correlating the lower Cambrian. Here we report SSF associations from the Yanjiahe Formation in the Three Gorges area, South China. The Yanjiahe Formation is well exposed near the Yanjiahe village, and its 40-m-thick sequence can be subdivided on the basis of lithology into five stratigraphic intervals (beds). Small shelly fossils occur mainly in Beds 2 and 5, but abundant SSFs were discovered in thin sections of siliceous–phosphatic nodules from Bed 3 for the first time. No skeletal fossils were discovered in the basal siliceous rock interval (Bed 1), but the negative δ13Ccarb excursion and the occurrence of the acritarch Micrhystridium regulare indicate that it belongs to the basal Cambrian. The SSF associations are somewhat similar to those of East Yunnan, and can be differentiated into three biozones (in ascending order): the Anabarites trisulcatus–Protohertzina anabarica assemblage zone (Bed 2), the Purella antiqua assemblage zone (Bed 3), and the Aldanella yanjiaheensis assemblage zone (Bed 5). The occurrence of A. yanjiaheensis in Bed 5 probably indicates that Bed 5 belongs to Cambrian Stage 2, but the Stage 2/Stage 1 boundary is uncertain since Bed 4 lacks fossils. SSF biostratigraphy indicates that the Yanjiahe Formation is pretrilobitic Meishucunian in age (equivalent to the Nemakit–Daldynian to Tommotian of Siberia, Terreneuvian). Five SSF genera occur in Bed 2, more than six genera in Bed 3, and twenty-three genera in Bed 5. The stepwise increase in generic diversity through the Yanjiahe Formation is comparable with the global diversity increase through the Nemakit–Daldynian to early Tommotian interval. 相似文献
12.
QIU Hao FENG Lianjun CHU Xuelei LI Luoyang ZHANG Xingliang LI Jinhua 《《地质学报》英文版》2022,96(4):1294-1307
Silica-phosphatic nodules are abundant in black shales of the Yanjiahe Formation in the Three Gorges Area of South China, which is correlated to the Fortunian Stage, Terreneuvian Series, Cambrian System. The nodules are rich in small shelly fossils and hence attract the attention of numerous paleontologists and sedimentary geologists. However, the genesis of the nodules and the preservation of the small shelly fossils are poorly understood. Here we analyze morphological, structural, mineralogical and chemical features of the nodules in multiscale using a combination of micro-X-ray fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy and confocal laser Raman spectroscopy. Results reveal that nodules are concentric in chemical and mineralogical compositions, comprising a silica-phosphatic core encrusted sequentially by a phosphatic zone, a siliceous zone and a very thin pyrite outer rim. The black shales hosting the nodules demonstrate a laminated texture of alternating clayey and silty laminae, which were respectively deposited in sulfidic/less sulfidic, high/low production, intense/weak chemical weathering conditions. The phosphogenesis of the nodules resulted in the phosphatization of small shelly fossils, which prevented the fossils from being dissolved during diagenesis, whereas the silica encrustation sealed the fossils within the nodules and thus protected the fossils from alteration by deep burial and surface weathering. 相似文献
13.
PENG Shanchi ZHU Xuejian ZUO Jinxun LIN Huanling CHEN Yong’an WANG Longwu 《《地质学报》英文版》2011,85(2):296-308
This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata. The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata. 相似文献
14.
本文报道新疆阿克苏地区寒武纪幸运期最早期的小壳化石组合。化石产自玉尔吐斯组底部,包括：Protohertzina anabarica Missarzhevsky, 1973、Protohertzina unguliformis Missarzhevsky, 1973、Anabarites trisulcatus Voronova and Missarzhevsky, 1969、Anabarites ternarius Missarzhevsky in Rozanov et al., 1969、Cambrotubulus decurvatus Missarzhevsky in Rozanov et al., 1969、Olivooides sp.、Kaiyangites novilis Qian and Yin, 1984以及海绵骨针化石。据此可以在新疆阿克苏地区玉尔吐斯组下部建立Anabarites trisulcatus-Protohertzina unguliformis组合带。该组合带下界以Anabarites trisulcatus、Protohertzina ungulifo... 相似文献
15.
A New Species of Septuconularia (Hexangulaconulariidae, Cnidaria) from Cambrian Stage 2, South China
SONG Zuchen GUO Junfeng HAN Jian Heyo VAN ITEN QIANG Yaqin PENG Jiaxin SUN Jie ZHANG Zhifei 《《地质学报》英文版》2022,96(3):757-765
Hexangulaconulariids, an extinct family of medusozoan small shelly fossils (SSFs), were a conspicuous component of early Cambrian, shallow marine platform communities in South China. Described herein is Septuconularia crassiformis sp. nov. from Bed 5 of the Yanjiahe Formation (Cambrian Stage 2) in the Three Gorges area of Hubei Province. The new species differs from the type and only other known species, S. yanjiaheensis, in the shape of the abapical portion and in the degree of curvature of the adapertural margin. The anatomy of the apical portion of the new species is unknown. The diagnosis of the genus Septuconularia is emended and the spatio-temporal distribution of hexangulaconulariids in South China is summarized. Finally, S. yanjiaheensis, with its slit-like aperture and very narrow transverse cross-section, may have been better adapted to the shallow platform environment than the broader S. crassiformis, which appears to have been less common than the type species. 相似文献
16.
宁镇山脉小壳化石层时代的新认识 总被引：2，自引：1，他引：2
最新研究表明，句容仑山的小壳化石层和南京幕府山的一样，其层位都相当于下寒武统沧浪铺阶Ｐａｏｋａｎｎｉａ带，为我国下寒武统层位最高的一个小壳化石组合带。句容仑山当时位于台地边缘，缺失了早寒武世早期至沧浪铺期中期的沉积。 相似文献
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18.
This work deals with the evolution of carbon isotope composition in the Luoyixi (罗依溪) Section, a candidate of the Global Standard Stratotype-section and Point (GSSP), defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge laevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy (ISCS) as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C, δ13O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values. 相似文献